Brigotti Maurizio, Carnicelli Domenica, Ravanelli Elisa, Vara Antonio González, Martinelli Chiara, Alfieri Roberta R, Petronini Pier Giorgio, Sestili Piero
Dipartimento di Patologia Sperimentale, Università di Bologna, Bologna, Italy.
Infect Immun. 2007 May;75(5):2201-7. doi: 10.1128/IAI.01707-06. Epub 2007 Feb 12.
Treatment of human endothelial cells with Shiga toxin 1 and 2 leads to the upregulation of genes encoding proinflammatory molecules involved in the pathogenesis of hemolytic-uremic syndrome. The paradoxical effect of inhibitors of mRNA translation, such as Shiga toxins, that at the same time induce protein expression was investigated by studying the relationship between their enzymatic activity (abstraction of adenine from nucleic acids) and the induction of interleukin-8 and granulocyte-macrophage colony-stimulating factor in human endothelial cells. As a positive control, the fungal toxin alpha-sarcin, acting on the same rRNA sequence targeted by Shiga toxins with a different mechanism (RNase activity), was used. The three toxins caused ribosomal lesions that, in turn, induced the activation of p38 stress kinase with kinetics that paralleled the inhibition of translation. Alpha-sarcin was devoid of activity on DNA. Shiga toxin 2 targeted nuclear DNA with more rapid kinetics than did Shiga toxin 1. Since the fungal ribotoxin was fully effective in the induction of proinflammatory proteins, we conclude that damage to ribosomes is indispensable and sufficient to activate protein expression via induction of the stress-kinase cascade. However, gene upregulation events induced by Shiga toxin 2 were much more efficient than those triggered by Shiga toxin 1, although the two toxins impaired translation to the same extent and had overlapping time courses of stress kinase activation. Regulations independent of the ribotoxic stress were assumed to operate in intoxicated cells. We hypothesized that the two bacterial toxins recognize different DNA sequences inducing different regulating effects on gene expression.
用志贺毒素1和2处理人内皮细胞会导致编码参与溶血尿毒综合征发病机制的促炎分子的基因上调。通过研究它们的酶活性（从核酸中提取腺嘌呤）与人内皮细胞中白细胞介素-8和粒细胞-巨噬细胞集落刺激因子诱导之间的关系，对mRNA翻译抑制剂（如志贺毒素）同时诱导蛋白质表达的矛盾效应进行了研究。作为阳性对照，使用了真菌毒素α-肌动蛋白，它以不同机制（核糖核酸酶活性）作用于志贺毒素靶向的相同rRNA序列。这三种毒素导致核糖体损伤，进而诱导p38应激激酶活化，其动力学与翻译抑制平行。α-肌动蛋白对DNA无活性。志贺毒素2比志贺毒素1更快地靶向核DNA。由于真菌核糖毒素在诱导促炎蛋白方面完全有效，我们得出结论，核糖体损伤对于通过诱导应激激酶级联反应激活蛋白质表达是必不可少且充分的。然而，志贺毒素2诱导的基因上调事件比志贺毒素1引发的事件效率高得多，尽管这两种毒素对翻译的损害程度相同，且应激激酶活化的时间进程重叠。假定在中毒细胞中存在与核糖毒性应激无关的调节作用。我们假设这两种细菌毒素识别不同的DNA序列，从而对基因表达产生不同的调节作用。
